RSQRTPS - Compute Reciprocals of Square Roots of Packed Single Precision Floating-Point Values

Opcode*/ Instruction

Op/ En

64/32 bit Mode Support

CPUID Feature Flag

Description

NP 0F 52 /r

RSQRTPS xmm1, xmm2/m128

RM

V/V

SSE

Computes the approximate reciprocals of the square roots of the packed single precision floating-point values in xmm2/m128 and stores the results in xmm1.

VEX.128.0F.WIG 52 /r

VRSQRTPS xmm1, xmm2/m128

RM

V/V

AVX

Computes the approximate reciprocals of the square roots of packed single precision values in xmm2/mem and stores the results in xmm1.

VEX.256.0F.WIG 52 /r

VRSQRTPS ymm1, ymm2/m256

RM

V/V

AVX

Computes the approximate reciprocals of the square roots of packed single precision values in ymm2/mem and stores the results in ymm1.

Instruction Operand Encoding

Op/En

Operand 1

Operand 2

Operand 3

Operand 4

RM

ModRM:reg (w)

ModRM:r/m (r)

N/A

N/A

Description

Performs a SIMD computation of the approximate reciprocals of the square roots of the four packed single precision floating-point values in the source operand (second operand) and stores the packed single precision floating-point results in the destination operand. The source operand can be an XMM register or a 128-bit memory location. The

destination operand is an XMM register. See Figure 10-5 in the Intel® 64 and IA-32 Architectures Software Devel- oper's Manual, Volume 1, for an illustration of a SIMD single precision floating-point operation.

The relative error for this approximation is:

|Relative Error| <= 1.5 * 2 - 12

The RSQRTPS instruction is not affected by the rounding control bits in the MXCSR register. When a source value is

a 0.0, an inf of the sign of the source value is returned. A denormal source value is treated as a 0.0 (of the same

sign). When a source value is a negative value (other than - 0.0), a floating-point indefinite is returned. When a source value is an SNaN or QNaN, the SNaN is converted to a QNaN or the source QNaN is returned.

In 64-bit mode, using a REX prefix in the form of REX.R permits this instruction to access additional registers (XMM8-XMM15).

128-bit Legacy SSE version: The second source can be an XMM register or an 128-bit memory location. The desti- nation is not distinct from the first source XMM register and the upper bits (MAXVL-1:128) of the corresponding YMM register destination are unmodified.

VEX.128 encoded version: the first source operand is an XMM register or 128-bit memory location. The destination operand is an XMM register. The upper bits (MAXVL-1:128) of the corresponding YMM register destination are zeroed.

VEX.256 encoded version: The first source operand is a YMM register. The second source operand can be a YMM register or a 256-bit memory location. The destination operand is a YMM register.

Note: In VEX-encoded versions, VEX.vvvv is reserved and must be 1111b, otherwise instructions will #UD.

Operation

RSQRTPS (128-bit Legacy SSE Version) 

DEST[31:0] := APPROXIMATE(1/SQRT(SRC[31:0]))
DEST[63:32] := APPROXIMATE(1/SQRT(SRC1[63:32]))
DEST[95:64] := APPROXIMATE(1/SQRT(SRC1[95:64]))
DEST[127:96] := APPROXIMATE(1/SQRT(SRC2[127:96]))
DEST[MAXVL-1:128] (Unmodified)

VRSQRTPS (VEX.128 Encoded Version) 

DEST[31:0] := APPROXIMATE(1/SQRT(SRC[31:0]))
DEST[63:32] := APPROXIMATE(1/SQRT(SRC1[63:32]))
DEST[95:64] := APPROXIMATE(1/SQRT(SRC1[95:64]))
DEST[127:96] := APPROXIMATE(1/SQRT(SRC2[127:96]))
DEST[MAXVL-1:128] := 0

VRSQRTPS (VEX.256 Encoded Version) 

DEST[31:0] := APPROXIMATE(1/SQRT(SRC[31:0]))
DEST[63:32] := APPROXIMATE(1/SQRT(SRC1[63:32]))
DEST[95:64] := APPROXIMATE(1/SQRT(SRC1[95:64]))
DEST[127:96] := APPROXIMATE(1/SQRT(SRC2[127:96]))
DEST[159:128] := APPROXIMATE(1/SQRT(SRC2[159:128]))
DEST[191:160] := APPROXIMATE(1/SQRT(SRC2[191:160]))
DEST[223:192] := APPROXIMATE(1/SQRT(SRC2[223:192]))
DEST[255:224] := APPROXIMATE(1/SQRT(SRC2[255:224]))

Intel C/C++ Compiler Intrinsic Equivalent 

RSQRTPS __m128 _mm_rsqrt_ps(__m128 a)
RSQRTPS __m256 _mm256_rsqrt_ps (__m256 a);

SIMD Floating-Point Exceptions

None.

Other Exceptions

See Table 2-21, "Type 4 Class Exception Conditions," additionally:

#UD

If VEX.vvvv != 1111B.